The invention herein described was made in the course of or under a contract with the United States Air Force Systems Command.
This invention relates to the isomerization of a saturated endo-endo dimer of norbornadiene, hereinafter referred to as HNN. Particularly the invention relates to the preparation of a solid isomeric mixture from liquid HNN involving a catalyst.
The aforementioned solid isomeric mixture can be used as a high energy missile fuel in either jet or rocket propulsion or as an additive for other similar mixtures. Jet propulsion includes a jet engine which can be used for a missile, an aircraft and others and includes the three basic types, i.e. ramjet, turbojet and pulse jet. The term rocket generally refers to a device containing fuel incorporating its own oxygen or oxidizing agent.
Norbornadiene (bicyclo-(2.21.1)-2,5-heptadiene) can be prepared by reacting cyclopentadiene and acetylene at an elevated temperature, see U.S. Pat. No. 2,875,256 (Cl 260-666). Norbornadiene has the following structure: ##STR1## It can be dimerized into an olefinic endo-endo homo dimer having the following structure: ##STR2## Dimerization of norbornadiene to compound I is disclosed in "The Stereochemical Course of Metal Catalyzed Cycloaddition Reactions of Norbornadiene", T. J. Katz et al, Tetrahedron Letters, No. 27, pp 2601-2605, 1967. The dimerization involves the use of a group VIII metal complex. Compound I is also disclosed in Chemical Abstracts, 91: 1, Jan. 1, 1969, page 265, 87128q. The dimerization is also disclosed in "Dimerization and Trimerization of Norbornadiene by Soluble Rhodium Catalysts", Nancy Acton et al, Journal of the American Chemical Society, 94:15, July 26, 1972.
The olefinic bond of compound I can be hydrogenated. Generally a hydrogenation catalyst such as 5% rhodium-on-alumina is satisfactory. The temperature and pressure used for hydrogenation can be mild, e.g. about 125.degree. C. and 100 psig of hydrogen. The saturated endo-endo dimer of norbornadiene (HNN) has the following structure: ##STR3##
Related work in catalytic isomerization of dimers of norbornadiene are reported in Journal of Catalyst 26, 333-337, 1972, "Skeletal Rearrangement of Some Cyclic Hydrocarbons Catalyzed by Palladium", H. A. Quinn et al; Journal of the American Chemical Society, 96:1, Jan. 9, 1974, "Hydrogenolysis of Substituted Nortricyclenes over Supported Metal Catalyst Methyl Migrations and Skeletal Rearrangements," M. N. Aktar et.al. Both of the foregoing involve the use of metals such as platinum or palladium as a catalyst.